Management Detail

Dagger Nematode

Reason for Concern:1) Nematodes, when present in large numbers, cause stunting and reduce vigor by feeding on the roots.
2) Dagger nematodes can transmit viruses.
Several nematode species have been associated with unthrifty blueberry plantings. However, there is no data on their roles in damaging new or established blueberry plantings.
3) Several nematode species have been associated with unthrifty blueberry plantings. However, there is no data on their roles in damaging new or established blueberry plantings.

Symptoms/Identification:
The usual symptoms are areas in the field of distorted or stunted plants. Most nematodes are microscopic though a few species can be seen without magnification. Most plant-parasitic nematodes would range in size from 0.02 to 0.04 inch in length. A great many nematodes have a wormlike or eellike shape. Females of some kinds grow swollen at maturity and resemble tiny beans, lemons, or pears.

Lifecycle:
Nematodes commonly have 6 developmental phases including an egg, 4 juvenile stages, and an adult nematode stage. Each juvenile stage is completed by a developmental process called a molt. Except for size, juveniles usually resemble adults. Reproductive organs normally do not appear until after the nematode has undergone 4 molts. Nematodes are present and active in the soil all year, although the level of activity will be the least in the winter when soils are cold.

Sample for Dagger nematodes December through March when their populations are highest.

Since they vector viruses, the population threshold is very low.

Cultural Controls:

It is important to consider the plant source. Virus-free planting material is essential for good establishment and for good productivity throughout the life of the planting.

Crop rotation: Plant blueberries in soil that has been fallow for at least two years.

Organic matter: Maintaining high levels of organic matter (sawdust or other mulch) in the soil will suppress plant-parasitic nematode population densities.

Site selection: Plant in soil that has been tested and found free of dagger nematodes.

Cover crops: Grow grass or Brassica (rapeseed, mustard) crops, which are not hosts for tomato ringspot virus and are poor hosts for dagger nematode, for one year. (To be successful, these crops need to be maintained free of broadleaf weeds that are hosts for the virus.) Cover crops such as marigolds, forage pearl millet (Canadian Forage Pearl Millet Hybrid 101), or Saia oats can help reduce populations of the root-lesion nematode.